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Int. J. Environ. Res. Public Health 2006, 3(3), 292-300; doi:10.3390/ijerph2006030036
Article

Microbial Diversity and Bioremediation of a Hydrocarbon-Contaminated Aquifer (Vega Baja, Puerto Rico)

1, 1, 3, 2,3 and 1,*
1 Department of Biology, University of Puerto Rico, P.O. Box 9012, Mayagüez, PR 00681, Puerto Rico 2 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA 3 Institute for Environmental Genomics and Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA
* Author to whom correspondence should be addressed.
Received: 15 November 2005 / Accepted: 3 July 2006 / Published: 30 September 2006
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Abstract

Hydrocarbon contamination of groundwater resources has become a major environmental and human health concern in many parts of the world. Our objectives were to employ both culture and culture-independent techniques to characterize the dynamics of microbial community structure within a fluidized bed reactor used to bioremediate a diesel-contaminated groundwater in a tropical environment. Under normal operating conditions, 97 to 99% of total hydrocarbons were removed with only 14 min hydraulic retention time. Over 25 different cultures were isolated from the treatment unit (96% which utilized diesel constituents as sole carbon source). Approximately 20% of the isolates were also capable of complete denitrification to nitrogen gas. Sequence analysis of 16S rDNA demonstrated ample diversity with most belonging to the ∝, β and γ subdivision of the Proteobacteria, Bacilli, and Actinobacteria groups. Moreover, the genetic constitution of the microbial community was examined at multiple time points with a Functional Gene Array (FGA) containing over 12,000 probes for genes involved in organic degradation and major biogeochemical cycles. Total community DNA was extracted and amplified using an isothermal φ29 polymerase-based technique, labeled with Cy5 dye, and hybridized to the arrays in 50% formimide overnight at 50°C. Cluster analysis revealed comparable profiles over the course of treatment suggesting the early selection of a very stable microbial community. A total of 270 genes for organic contaminant degradation (including naphthalene, toluene [aerobic and anaerobic], octane, biphenyl, pyrene, xylene, phenanthrene, and benzene); and 333 genes involved in metabolic activities (nitrite and nitrous oxide reductases [nirS, nirK, and nosZ], dissimilatory sulfite reductases [dsrAB], potential metal reducing C-type cytochromes, and methane monooxygenase [pmoA]) were repeatedly detected. Genes for degradation of MTBE, nitroaromatics and chlorinated compounds were also present, indicating a broad catabolic potential of the treatment unit. FGA’s demonstrated the early establishment of a diverse community with concurrent aerobic and anaerobic processes contributing to the bioremediation process.
Keywords: Bioremediation; functional gene microarray; biofilm; tropical environments Bioremediation; functional gene microarray; biofilm; tropical environments
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Rodríguez-Martínez, E.M.; Pérez, E.X.; Schadt, C.W.; Zhou, J.; Massol-Deyá, A.A. Microbial Diversity and Bioremediation of a Hydrocarbon-Contaminated Aquifer (Vega Baja, Puerto Rico). Int. J. Environ. Res. Public Health 2006, 3, 292-300.

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